Human Physiology. 121 



-made suckers, or vacuum pumps, which fasten themselves to 

 everything they touch, until the animal chooses to relax the 

 muscles which control them. There does not probably exist 

 an animal at once so hideous, so powerful, and so voracious. 



Of the numerous tribes of crustaceans, the lobster may be 

 taken as an example, with his protective coat of mail, strong, 

 yet yielding to every motion, so that he can swim twenty feet 

 backward with one downward stroke of his tail. As he cannot 

 move his head, his eyes are placed at the ends of two flexible 

 tubes which he bends every way. He has also long, jointed 

 feelers, and his great powerful claws, with which he seizes his 

 prey, are furnished with teeth to cut it in pieces. When the 

 lobster has outgrown his shell, he casts it off, pulling out his 

 legs as from so many boots, and soon grows a new one. The 

 cast shell contains the perfect mould of every part the eyes, 

 tht teeth, every spike, every hair; and all are reformed again 

 and again with the greatest perfection. Even crustaceans one 

 sixteenth of an inch long shed their shells to the minutest parts. 



Life in the insect world manifests a wonderful vigour of force 

 and variety of manifestations, with an infinity of the most 

 curious and astonishing contrivances. The nervous power and 

 muscular strength of insects greatly surpass those of larger 

 animals. 



Insects have six legs, two antennae or feelers, sometimes 

 folded up in protecting cases; from two to six simple eyes, and 

 two compound eyes, each composed of from 25 to 12,500 

 perfectly formed distinct organs of vision ; a brain and double 

 nervous system ; a heart and circulatory system with numerous 

 valves; air-tubes spread through the whole body, two trachae 

 with 236 tubes and 1,004 branches; jaws armed with hooks, 

 sharp shears for cutting vegetable substances, saws, files, 

 augers, lancets, sucking tubes; stings in sheaths, spirting 

 poison secreted by glands and kept in proper receptacles; 

 liquid silk and the machinery for spinning it; eggs and instru- 



